Disclosed herein is an apparatus and method that controls pressure roll flare in a print apparatus.
Presently, image output devices, such as printers, multifunction media devices, xerographic machines, ink jet printers, and other devices produce images on media sheets, such as paper, substrates, transparencies, plastic, labels, or other media sheets. To produce an image, marking material, such as toner, ink jet ink, or other marking material, is applied to a media sheet to create a latent image on the media sheet. A fuser assembly then affixes or fuses the latent image to the media sheet by applying heat and/or pressure to the media sheet.
Fuser assemblies apply heat and pressure using rotational members, such as fuser rolls or belts, that are coupled to each other at a fuser nip. The rotational members apply heat and pressure to the media sheet with the latent image as the media sheet is fed through the fuser nip to affix the image to the media sheet.
Some fuser rolls are flared to reduce wrinkling of media sheets in the fuser nip. In particular, the fuser roll or pressure roll is flared by having a wider diameter at its outside paper path portion than the diameter at its inside paper path portion. This flare provides a tentering force on media sheets to reduce wrinkle of the media sheets as they pass through the fuser nip. It is useful to have a fuser roll with a predictable flare.
Unfortunately, the fuser or pressure roll flare changes between standby operation and steady state print job operation. This change is caused by a thermal differential between the fuser roll inside paper path and the fuser roll outside paper path, which is caused by media sheets cooling the pressure roll inside paper path during a print job. For example, the pressure roll has a room temperature flare. The diameter of the pressure roll inside paper path reduces as media sheets cool the inside paper path of the pressure roll while the outside paper path diameter grows as the fusing belt cools the outside paper path of the pressure roll during a print job, which increases the pressure roll flare. Thus, the pressure roll may have insufficient flare to reduce wrinkling of the first media sheets at the beginning of a print job before the fuser temperatures settle to steady state operation. Furthermore, the pressure roll may also achieve excessive flare during the print job when the media sheets cool the inside paper path. This excessive flare produces an undesirable result of smeared images on the media sheets.
Thus, there is a need for an apparatus and method that controls pressure roll flare in a print apparatus.